Mutant IDH inhibits HNF-4α to block hepatocyte differentiation and promote biliary cancer

Mutations in isocitrate dehydrogenase 1 (IDH1) and IDH2 are among the most common genetic alterations in intrahepatic cholangiocarcinoma (IHCC), a deadly liver cancer1, 2, 3, 4, 5. Mutant IDH proteins in IHCC and other malignancies acquire an abnormal enzymatic activity allowing them to convert α-ketoglutarate (αKG) to 2-hydroxyglutarate (2HG), which inhibits the activity of multiple αKG-dependent dioxygenases, and results in alterations in cell differentiation, survival, and extracellular matrix maturation6, 7, 8, 9, 10. However, the molecular pathways by which IDH mutations lead to tumour formation remain unclear. Here we show that mutant IDH blocks liver progenitor cells from undergoing hepatocyte differentiation through the production of 2HG and suppression of HNF-4α, a master regulator of hepatocyte identity and quiescence. Correspondingly, genetically engineered mouse models expressing mutant IDH in the adult liver show an aberrant response to hepatic injury, characterized by HNF-4α silencing, impaired hepatocyte differentiation, and markedly elevated levels of cell proliferation. Moreover, IDH and Kras mutations, genetic alterations that co-exist in a subset of human IHCCs4, 5, cooperate to drive the expansion of liver progenitor cells, development of premalignant biliary lesions, and progression to metastatic IHCC. These studies provide a functional link between IDH mutations, hepatic cell fate, and IHCC pathogenesis, and present a novel genetically engineered mouse model of IDH-driven malignancy

Proto-Oncogenic Role of Mutant IDH2 in Leukemia Initiation and Maintenance

Mutations in the metabolic enzymes isocitrate dehydrogenase-1 (IDH1) and IDH2 that produce the oncometabolite D-2-hydroxyglutarate (2-HG) occur frequently in human acute myeloid leukemia (AML). 2-HG modulates numerous biological pathways implicated in malignant transformation, but the contribution of mutant IDH proteins to maintenance and progression of AML in vivo is currently unknown. To answer this crucial question we have generated transgenic mice that express IDH2R140Q in an on/off- and tissue-specific manner using a tetracycline-inducible system. We found that IDH2R140Q can cooperate with overexpression of HoxA9 and Meis1a and with mutations in FMS-like tyrosine kinase 3 (FLT3) to drive acute leukemia in vivo. Critically, we show that genetic deinduction of mutant IDH2 in leukemic cells in vivo has profound effects on their growth and/or maintenance. Our data demonstrate the proto-oncogenic role of mutant IDH2 and support its relevance as a therapeutic target for the treatment of human AML.Stem Cell and Regenerative Biolog